The present invention relates to the field of butterfly valves, and more particularly, to large diameter butterfly valves for use in corrosive and/or high temperature environments.
Many industrial operations produce or require large volumetric flows of corrosive and/or high temperature gases. Flow control is often provided by means of large diameter butterfly valves. In general, it is desirable that these butterfly valves include a relatively lightweight valve closure plate which is durable and corrosion resistant, together with a durable, fluid tight seal between valve closure plate and the valve housing of the butterfly valve. To obtain a fluid tight seal, current large diameter butterfly valves generally employ one of two sealing configurations, both utilizing an elastomeric O-ring adjacent the periphery of the valve closure plate. A first type uses an O-ring seal seated in an annular groove disposed on the periphery of the valve closure plate, while a second type uses an O-ring seal seated in an annular groove disposed on the valve housing of the butterfly valve. In both sealing configurations, as the valve closure plate is rotated to a closed position, the elastomeric O-ring contacts a corresponding surface on, in the former seal configuration, the valve housing or, in the latter, the periphery of the valve closure plate. This causes the O-ring to resiliently compress along its entire circumference to form a fluid tight seal between the closure plate and the housing. While both of the above seal configurations can provide acceptable seals, they have proved susceptible to the same problem--the lateral forces imposed on the O-ring seal during the opening and closing sequences of the closure plate tend to cause the O-ring seal to roll out of its annular groove, separating it from its seat and destroying the seal.
Therefore, a general object of the present invention is to provide an improved structure for a large diameter butterfly valve.
A further object of the present invention is to provide an improved seal configuration for the valve closure plate which is fluid tight and durable.
Yet a further object of the present invention is to provide such a seal configuration fabricated from an elastomeric material which can be securely affixed to the valve structure and is not susceptible to being dislodged from its sealing position upon repeated opening and closing of the valve.
Another object of the present invention is to provide such a valve closure plate which is fabricated from lightweight, durable and corrosion resistant materials.